This practice, instituted in 1981, was intended to fight car theft in two ways: It let a vehicle's original VIN be located even if a different dash tag was substituted (to re-title a stolen car), and it let law enforcement officers identify the source of parts stolen from vehicles later dismantled in "chop shops" for their engines, transmissions, and major body panels.

Today, VINs may be found on a vehicle's dash panel, firewall, engine, steering column, radiator-support bracket, door or door post, inner fender liner, or other places--depending on manufacturer.

Some car-theft experts even advise etching a vehicle's VIN onto the windows, on the theory that it will deter thieves who would have to replace every window to resell it if stolen.

In the case of the Times Square Pathfinder, New York Police Department Detective John Wright found the VIN on its engine block.

That led officers to the vehicle's Connecticut title, and its last registered owner, who had sold it to Shahzad via Craigslist. The telephone number Shahzad gave the previous owner proved to be the break they needed.